Truck-mounted brake system

ABSTRACT

A truck mounted braking system is provided with a mechanical pivot adjustment on a lever connected to the brake actuator to permit the braking force applied to the wheels to vary depending on the lading condition of the car, without involving additional pneumatic elements such as a pneumatic empty load device. The system adjusts the braking force applied when the hand brake is activated, even when the railway car is disconnected from the pneumatic brake line.

FIELD OF THE INVENTION

The invention relates to braking systems for a railway car andimprovements thereof and particularly to truck-mounted braking systems.

BACKGROUND OF THE INVENTION

The conventional railway car truck in use in North America for severaldecades has been the three-piece truck, comprising a pair of parallelside frames oriented longitudinally and connected by a transverselymounted bolster. The bolster is supported on the side frames by springsets. The wheel sets of the truck are received in bearing adaptersplaced in leading and trailing pedestal jaws in the side frame. Therailway car is mounted on the center plate of the bolster, which allowsthe truck to pivot with respect to the car.

Braking systems for the railway car transmit force from a pneumatic orhydraulic actuator to cause the brake shoes to be applied against thewheels. Such systems may comprise “foundational” rigging, havingcomponents distributed on the railway car, or alternatively, may bemounted on the truck in a truck-mounted system. In either case, there isalways a premium on the available space on the car body or on the truckfor the necessary components so that the parts do not interfere withother systems on the railway car.

A truck-mounted braking system typically comprises two brake beamstransversely mounted with respect to a longitudinal axis of the railwaycar and having brake shoes on opposite ends. Each brake beam typicallycomprises a compression member and a tension member connected in themiddle by a strut. The brake beams may be connected by a brake actuatorassembly comprising an actuator (such as an air cylinder) mounted on oneof the beams, and a push rod oriented longitudinally between the brakebeams, so that when the brake is applied, the brake actuator assemblyforces the beams apart, causing force to be transmitted to the brakeshoes which press against the wheels. The truck-mounted system ischaracterized by having fewer elements between the brake actuator andthe wheels, compared to a foundational rigging system.

A conventional truck-mounted brake system may also comprise a slackadjuster assembly, as disclosed in U.S. Patent Application PublicationNo. 2016/0229428 to Sunde, which is incorporated by reference in itsentirety. The slack adjuster may be mounted in tandem with the brakeactuator assembly, such that the brake actuator assembly and the slackadjuster are connected to the respective brake beams by a pair oflevers. The slack adjuster transmits force between the brake beams andadjusts the distance between the brake beams to accommodate for wear onthe brake pads. It is characteristic of the truck-mounted systems thatthe slack adjuster and the brake actuator are situated between thelevers on opposed brake beams.

Braking ratio is the ratio of braking force applied on the railway carwheels to the weight of the railway car. The American Association ofRailroads (“AAR”) sets a standard (AAR S-401-99) for the brake ratio fora loaded car at a maximum of 14%, and for an empty car at 32%. Inaddition, the AAR requires a minimum braking ratio of 11% for an airbrake and 10% for a hand brake. The danger of exceeding braking ratiosis that the brake shoes may become locked against the wheels, so thatthe wheels fail to turn and are pushed along the rails. Therefore, it isdesired to be able to adjust the brake force applied against the wheelsdepending on the lading condition of the railway car.

Braking systems for railway cars universally include a hand brake,operated manually and independently of the pneumatic brake system. Ahand brake for a foundational brake rigging system is described in U.S.Pat. No. 7,896,140 to Heitmeyer, incorporated by reference. A hand brake(and hand brake lever) for a truck-mounted braking system is describedin U.S. Pat. No. 6,702,073 to Sommerfeld, also incorporated byreference. In a truck-mounted system, the hand brake may be connected toone end of the live lever, actuated manually, usually to secure anunattended or unpowered car against unplanned movement, i.e., as a“parking brake”. Thus the hand brake is capable of operating even whenthe pneumatic brake is not on line. Conventionally, the hand brakeapplies the same force to the wheels whether the car is loaded orunloaded, being independent of the brake pneumatics.

So-called “empty load devices” are known which operate in conjunctionwith pneumatic systems, to maintain braking forces below a certain brakeratio depending on the sensed weight of the car. U.S. Pat. No.4,080,005, which is incorporated by reference, discloses an empty loadfluid pressure brake system with a proportioning valve, operated withcompressed air. By way of example and not limitation, a mechanical emptyload device used with a foundational brake rigging system is disclosedin U.S. Pat. No. 3,690,420 to Natschke, which is also incorporated byreference. The braking systems disclosed in this patent is characterizedby an outboard arrangement of the load sensing device and the brakeactuator.

Further examples of a truck-mounted braking system of the type describedabove are provided in U.S. Patent Application Publication No.2011/0147140 to Ring, and U.S. Pat. No. 7,802,662, also incorporated byreference in their entirety. These additional disclosures teach variousmethods and apparatuses for preventing or limiting brake lock-out andfor monitoring and controlling travel of the brake elements generally.

SUMMARY OF THE INVENTION

Railway cars have become lighter and the laded weights of the cars havebecome heavier over time. Therefore, it is desired to improve theefficiency with which a different brake load is applied to the brakes inan empty car versus a fully loaded car.

In one aspect, the invention is a mechanical brake ratio adjustmentmechanism for a truck-mounted braking system.

In another aspect, the invention achieves brake ratio adjustment basedon the lading condition of a railway car while avoiding the use of apneumatically operated empty load device, relying instead on amechanical adjustment based on the loaded or unloaded condition of therailway car.

In still another aspect, the invention alters the braking force appliedto the wheels when a manually operated hand brake is applied, based on amechanical pivot adjustment of the brake lever depending on the ladingcondition of the railway car, independently of whether a pneumatic brakesystem is on-line.

These and other objects of the invention may be achieved with atruck-mounted braking system for a railway car, wherein a first brakebeam and a second brake beam are separated along a longitudinal axis ofthe railway car, the first and second brake beams each having acompression member and a tension member, and a respective first andsecond strut attached between the respective compression member andtension member. A brake actuator is mounted between the brake beams, anda brake actuator lever connection is connected to the brake actuator andadapted to move linearly in response to the brake actuator. A live leveris pivotally attached to the first strut on the first brake beam by apin, pivotally attached to the brake actuator lever connection, andpivotally attached at an end of the live lever to a slack adjuster. Adead lever is pivotally attached to the second strut on the second brakebeam, pivotally attached at one end to the slack adjuster, and pivotallyattached at an end opposite said one end, directly or indirectly, to thebrake actuator. A pivot adjustment hole is provided in the live leverand/or the dead lever to receive the pin in at least two differentpositions in the hole, corresponding to at least two lading conditionsof the railway car.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 schematically depicts a truck-mounted braking system according toan embodiment of the invention.

FIG. 2 is a view of the truck-mounted braking system from the topaccording to another embodiment of the invention, showing aninstallation on a railway car truck.

FIG. 3 depicts a live lever according to one embodiment of theinvention.

FIG. 4 is a view of a sensor assembly according to an embodiment of theinvention.

FIG. 5 is a cutaway view of a slack adjuster according to an embodimentof the invention.

DETAILED DESCRIPTION OF THE INVENTION

Directions and orientations herein may refer to the normal orientationof a railway car in use. Thus, unless the context clearly requiresotherwise, the “longitudinal” axis or direction is parallel to the railsand in the direction of movement of the railway car on the track ineither direction. The “transverse” or “lateral” axis or direction is ina horizontal plane perpendicular to the longitudinal axis and the rail.Individual components of a braking system may also have a length and“longitudinal axis”, a width and a “lateral axis”. Thus, a brake lever,for example, which is oriented substantially in line with thetransversely mounted brake beam, has a longitudinal axis of its own,which may be nearly perpendicular to the longitudinal axis of therailway car. The term “inboard” means toward the center of the car, andmay mean inboard in a longitudinal direction, a lateral direction, orboth. Similarly, “outboard” means away from the center of the car.“Vertical” is the up-and-down direction, and “horizontal” is a planeparallel to the rails including the transverse and longitudinal axes.

Specific dimensions in the railway industry are often established bystandards. Therefore, dimensions provided herein are intended to beapproximate and descriptive only, because it is understood thatultimately the given dimension may be altered or varied to accommodate aparticular AAR standard. In the same spirit, the word “about”, used incombination with a specific quantity, means+/−15%. The word“substantially” means all or completely, with some variation allowed forinevitable departure from exactitude as would be understood and acceptedby a person having ordinary skill in the art.

A truck-mounted braking system for a railway car according to oneembodiment of the invention is shown in FIG. 1, including a first brakebeam 15 and a second brake beam 115 separated along a longitudinal axisof the railway car. The ends of the brake beams 15, 115 are connected tobrake heads 22, and brake shoes 24. As shown in FIG. 2, when the breakbeams are forced away from each other when the brakes are applied, thebrake shoes apply force directly to the wheels 26. In embodiments, brakeshoes 24 are made removable from brake heads 22 using a clip 25. Inembodiments, tension member 121, 122 is mechanically secured to brakehead 22, such as with a nut 171.

The first and second brake beams 15, 115 each have a compression member123, 124 and a tension member 121, 122 and struts 14, 114 attachedbetween the respective compression member 123, 124 and tension member121, 122. In the embodiments shown, the brake actuator assembly includesan air cylinder 111, and an air cylinder push rod 216 operativelyconnected to the cylinder 111, adapted to move linearly in response topressure in the air cylinder. Other brake actuators, such as a rollingdiaphragm and an air bag are known in the art, and a person havingordinary skill in the art may adapt the construction of the brakingsystem according to the principles described herein for use with theseother types of brake actuators without departing from the scope of theinvention.

In the embodiment shown in FIG. 1, brake system 10 comprises live lever12 pivotally attached to first strut 14 by a pin 16 (called the “pivotpin”), and pivotally attached to the brake cylinder push rod 216(obscured behind lever 12 in FIG. 1) by a suitable connection, such as ayoke and pin 13 on the lever connection element. Slack adjuster bar 18is pivotally attached at an end of the live lever 12 on the oppositeside of the pivot pin. In the embodiment shown, slack adjuster bar 18 isattached to lever 12 with a similar yoke 19 and pin 17. Dead lever 112is pivotally attached to second strut 114, on opposing brake beam 115,pivotally attached at one end by pin 117 to the slack adjuster bar 18,and pivotally attached at the opposite end to the brake actuatorassembly via return push rod 119 using a similar connection.

Characteristic of a truck-mounted system, the lever arms applyingbraking force are significantly shorter than they would be on a typicalfoundation brake rigging. In a foundation brake rigging system, eachbrake lever arm, i.e., on either side of the pivot, may be on the orderof 18 inches. Adjusting the mechanical pivot point of such a large leverwhile maintaining precise operation poses a challenge. In contrast, thesmaller lever arm(s) of the truck-mounted system (on the order of about4-6 inches), allow for a more precise force adjustment. In theembodiment shown, dead lever 112 may be provided with one lever arm 112Elonger than the other arm 112A. For example, the lever arm 112B betweenthe slack adjuster 18 and pivot pin 116 through second strut 114 may belonger than the lever arm 112A between the return push rod 110 and pivotpin 116. In embodiments, it may be desirable to provide a pivot pinthrough hole on the dead lever that permits mechanical pivot adjustmentaccording to the lading condition of the railway car. This may be as analternative to, or in addition to, a pivot adjustment on the live lever,although less leverage is expected if the pivot adjustment is on thedead lever. In principle, the through hole can be provided in eitherlever. However, in the embodiment depicted in the Figures, the pivotadjustment having variable positions is on the live lever, as depictedin FIG. 3.

As shown in FIG. 3, the pivot adjustment hole 31 allows adjustment ofthe lever arm distance D1 between the pivot pin and the slack adjusterand the distance D2 between the pivot pin and the brake actuator. In theembodiment shown, pivot adjustment hole 31 is crescent-shaped, with arecess adapted to receive pin 16 in different positions on oppositeends. When the car is loaded, pivot pin 16 is received in recess 33, andthe lever arm D2 from the actuator to the pivot pin is longer than thelever arm D1 from the pivot pin to the slack adjuster. The larger momentarm results in a greater braking force being applied than when theactuator is closer to the pivot pin. A typical live lever in atruck-mounted brake system may have a length of about 12 inches betweenthe brake actuator and the slack adjuster (although that distance is notcritical to the invention). For a fully loaded car the distance betweenthe actuator and the pivot pin may be about 6 inches, and the distancebetween the pivot pin and the slack adjuster may be about 4.5 inches(these specific dimensions are by way of example and not by way oflimitation). When the car is unloaded, lever 12 shifts to a differentposition and pivot pin 16 is received in a different part of the throughhole. The lever arms are thereby reversed, and the lever arm between theactuator and the pivot pin is about 4.5 inches and the distance betweenthe pivot pin and the slack adjuster is about 6 inches, with the resultthat less braking force is transmitted to the wheels.

For example, and not by way of limitation, changing the pivot positionby the amounts indicated above may result in a decrease to about 68% ofa maximum braking force applied upon application of the hand brake in aloaded versus and unloaded railway car, and a decrease to about 56% of amaximum braking force applied upon application of the pneumaticallyactivated brakes. Changing the pivot point longitudinally on the livelever, even by a small amount, has a profound impact on the brakingratio, and this is achieved without the need for a pneumatic empty loaddetector and the associated piping.

As shown in FIG. 3, one end of the live lever may be characterized by ahand brake connection portion 34 opposite the end of the live leverconnected to slack adjuster 18. The hand brake connection portion 34 isat a different height and is positioned with respect to the brake beamto afford access and leverage to the hand brake (not shown) whenapplied. The live lever also includes a bend 35 in the longitudinaldirection so that the lever is approximately crescent shaped when viewedin plan layout. Pivot adjustment 31 is located on the live lever betweenthe slack adjuster connection 36 and the actuator connection 37, butoffset slightly with respect to a line drawn from the center of theslack adjuster connection 36 and the actuator connection 37. The overallshape of the pivot adjustment through hole 31 itself is crescent shaped.The embodiment depicted in FIG. 2 shows the live lever without ahandbrake connection.

The slack adjuster 18 itself, as shown in FIG. 5, may include a push rod52 and a spring 54, adapted to exert a varying force on the brake shoesto accommodate for brake pad wear during operation. A pawl mechanism 56is provided to ensure that the slack adjuster is neutral at rest. In theprior art, the pawl box 58 was typically welded on. An advantage isachieved by removably mounting the pawl box 58 on the slack adjusterouter housing, such that it can be easily assembled, non-destructivelyremoved, and repaired.

A mechanical sensor 40, adapted to detect the loaded condition of therailway car and change the position of the pivot adjustment hole of thelever may be mounted on the bolster as shown in FIG. 2, althoughplacement of the mechanical sensor may well vary depending on the truckdesign. In the embodiment shown, the mechanical sensor 40 comprises asensor arm 41 in contact with an upper spring seat window of side frame700, such that a loaded condition of the railway car corresponds to alarger space between the bolster and the side frame. Sensor arm 41communicates with a set of springs 43, 44 in the sensor housing thatprevents the pivot position from being altered when the brakes arealready locked out, if the car is loaded after the handbrake is applied,for example. Output arm 46 on the sensor assembly may be mechanicallyconnected to the live lever, rotating to apply force to the lever andalter the position of the pivot pin. Preferably, the mechanicalattachment of the output arm 46 to the live lever is proximate the pivotadjustment hole and is rigid, to enable movement of the lever by pullingand pushing (i.e., whether the member is in tension or in compression).

The description of the foregoing preferred embodiments is not to beconsidered as limiting the invention, which is defined according to theappended claims. The person of ordinary skill in the art, relying on theforegoing disclosure, may practice variants of the embodiments describedwithout departing from the scope of the invention claimed. A feature ordependent claim limitation described in connection with one embodimentor independent claim may be adapted for use with another embodiment orindependent claim, without departing from the scope of the invention.

What is claimed is:
 1. A truck-mounted braking system for a railway car,comprising, a first brake beam and a second brake beam separated along alongitudinal axis of the railway car, the first and second brake beamseach having a compression member and a tension member, and a respectivefirst and second strut attached between the respective compressionmember and tension member; a brake actuator; a brake actuator leverconnection operatively connected to the brake actuator and adapted tomove linearly in response to the brake actuator; a live lever pivotallyattached to the first strut on the first brake beam by a pin, pivotallyattached to the brake actuator lever connection, and pivotally attachedat an end of the live lever to a slack adjuster; a dead lever, pivotallyattached to the second strut on the second brake beam, pivotallyattached at one end to said slack adjuster, and pivotally attached at anend opposite said one end, directly or indirectly, to the brakeactuator; and a pivot adjustment hole in the live lever that receivesthe pin in at least two different positions in the hole, correspondingto at least two lading conditions of the railway car; wherein the pivotadjustment hole is a crescent-shaped aperture adapted to accommodate thepivot pin in said at least two positions at two opposed ends of thepivot adjustment hole.
 2. The truck mounted braking system according toclaim 1, wherein the live lever has a hand brake connection at one endadapted for mechanical connection to the hand brake.
 3. Thetruck-mounted braking system according to claim 2, wherein the handbrake connection has a raised height relative to the pivot adjustmenthole.
 4. The truck-mounted braking system according to claim 1, whereinan end of the live lever opposite the slack adjuster is angled away froma line drawn through the brake actuator lever connection and theattachment of the lever to the slack adjuster.
 5. The truck-mountedbraking system according to claim 1, further comprising a sensordetecting the at least two lading conditions of the railway car, thesensor mounted to the railway car truck and mechanically connected tothe live lever.
 6. The truck-mounted braking system according to claim5, wherein the sensor is mounted to a railway car bolster, and a leveron the sensor contacts a point on the side frame to detect a ladingcondition of the railway car.
 7. The truck-mounted braking systemaccording to claim 5, further comprising an output arm on the sensorhaving a rigid attachment to the live lever proximate the pivotadjustment hole, said attachment adapted to move the position of thepivot adjustment hole in tension and compression.
 8. The truck-mountedbraking system according to claim 1, wherein the slack adjuster includesa housing and a pawl box removably and mechanically mounted on thehousing.